In modern elevators, the position of the elevator car needs to be known for various reasons. For example, car position is typically used as a parameter based on which movement of the elevator car is controlled. There are various other uses for car position, such as uses related to safety and destination control algorithms.
In a conventional elevator, separate positioning switches are placed on each floor. These switches can indicate when the car is at their level and thereby position can be determined based on signals from said switches. In addition, elevators having long floor-to-floor—distances are provided with additional switches, so called dummy switches, in express zones that are between floors. This is the case for example with so called express or shuttle elevators.
Also such elevators have been proposed wherein the car position is determined based on encoded information. In US2006032711A1, a strip having a code mark pattern is placed to extend along a guide rail, which code mark pattern is read with a sensor device traveling with the car. An analyzer is provided for determining current car position based on the read code mark pattern. Closely related solutions are presented in WO03011733A1 and DE9210996U1. These solutions describe different alternative solutions for how the code mark pattern can be designed so that information can be read therefrom which enables determination of current position of the car. Said codes and alternative or corresponding codes are further known in general from encoder—devices. A drawback of these known solutions has been that a very long code pattern needs to be provided and installed accurately in the hoistway during installation process of the elevator. The installation process is time consuming as it needs to be done very accurately, and majority of the work needs to be performed at the installation site. Thereby, the installation process postpones completion of the new elevators and increases down time of the elevator being modernized.
In many elevator configurations it is difficult and laborious to fix the component comprising the code mark pattern in such a way that it is continuous and can be reliably sensed. Particularly, a drawback of known solutions is that the installation of the code mark pattern in the hoistway is challenging to carry out with good results, because the base on which the strip is to be added is difficult to make firm enough and immune to disturbances caused by car movement so that a reliable sensing can be obtained during movement of the car. For example, the guide rail lines are made of successive separate sections. Thereby, they are not firm and immune to disturbances, and thus provide a challenging base for the code mark pattern. Guide rail lines are also prone to deform during use of the elevator, whereby the code pattern is deformed as well.